1、BSI Standards PublicationBS ISO/IEC 18477-1:2015Information technology Scalable compression andcoding of continuous-tone stillimagesPart 1: Scalable compression and coding ofcontinuous-tone still imagesBS ISO/IEC 18477-1:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implement
2、ation of ISO/IEC18477-1:2015.The UK participation in its preparation was entrusted to TechnicalCommittee IST/37, Coding of picture, audio, multimedia andhypermedia information.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not p
3、urport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2015. Published by BSI StandardsLimited 2015ISBN 978 0 580 85832 1ICS 35.040Compliance with a British Standard cannot confer immunity fromlegal obligations
4、.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 July 2015.Amendments issued since publicationDate Text affectedBS ISO/IEC 18477-1:2015Information technology Scalable compression and coding of continuous-tone still images Part 1: Scalable c
5、ompression and coding of continuous-tone still imagesTechnologies de linformation Compression chelonnable et codage dimages plates en ton continu Partie 1: Codage des images gamme dynamique leveINTERNATIONAL STANDARDISO/IEC18477-1Reference numberISO/IEC 18477-1:2015(E)First edition2015-06-15 ISO/IEC
6、 2015BS ISO/IEC 18477-1:2015ii ISO/IEC 2015 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO/IEC 2015, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical
7、, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, Switzerla
8、ndTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgISO/IEC 18477-1:2015(E)BS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Symbols and abbreviated terms . 44.1 Symbols . 44.2 Abbreviated terms .
9、45 Conventions . 45.1 Conformance language . 45.2 Operators . 45.2.1 Arithmetic operators 45.2.2 Assignment operators . 55.2.3 Precedence order of operators 55.2.4 Mathematical functions . 56 General 56.1 General definitions 56.2 Functional overview on the decoding process 66.3 Encoder requirements
10、66.4 Decoder requirements 6Annex A (normative) Component subsampling and expansion of subsampling 7Annex B (normative) Codestream syntax 9Annex C (normative) Multi-component decorrelation .16Bibliography .18 ISO/IEC 2015 All rights reserved iiiContents PageBS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015
11、(E)ForewordISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through tech
12、nical committees established by the respective organization to deal with particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take pa
13、rt in the work. In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different app
14、roval criteria needed for the different types of document should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility that some of the elements of this document may be the subje
15、ct of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).An
16、y trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in t
17、he Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee responsible for this document is ISO/IEC JTC 1, Information technology, SC 29, Coding of audio, picture, multimedia and hypermedia information.ISO/IEC 18477 consists of the following parts,
18、under the general title: JPEG HDR image coding system: Part 1: Coding of high dynamic range images Part 2: Extensions for high dynamic range images Part 3: Box file format Part 6: IDR Integer Coding Part 7: HDR Floating-Point CodingThe following parts are under preparation: Part 4: Conformance testi
19、ng Part 5: Reference software Part 8: Coding of high dynamic range images Part 9: Encoding of alpha channelsiv ISO/IEC 2015 All rights reservedBS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E)IntroductionThis part of ISO/IEC 18477 specifies a coded codestream format for storage of continuous-tone photo
20、graphic content. JPEG XT is a scalable image coding system that builds on top of the legacy Rec. ITU-T T.81 | ISO/IEC 10918-1 coding system, also known as JPEG, but extends it in a backwards compatible way. This part of ISO/IEC 18477 specifies the commonly deployed components of the JPEG coding syst
21、em. Additional parts of ISO/IEC 18477 will extend on this baseline.JPEG XT has been designed to be backwards compatible to legacy applications while at the same time having a small coding complexity; JPEG XT uses, whenever possible, functional blocks of Rec. ITU-T T.81 | ISO/IEC 10918-1, Rec. ITU-T
22、T.86 | ISO/IEC 10918-4 and Rec. ITU-T T.871 | ISO/IEC 10918-5 to extend the functionality of the legacy JPEG Coding System. It is optimized for good image quality and compression efficiency while also enabling low-complexity encoding and decoding implementations. ISO/IEC 2015 All rights reserved vBS
23、 ISO/IEC 18477-1:2015BS ISO/IEC 18477-1:2015Information technology Scalable compression and coding of continuous-tone still images Part 1: Scalable compression and coding of continuous-tone still images1 ScopeThis part of ISO/IEC 18477 specifies a coding format, referred to as JPEG XT, which is desi
24、gned primarily for continuous-tone photographic content.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest
25、edition of the referenced document (including any amendments) applies.ISO/IEC 10918-1, Information technology Digital compression and coding of continuous-tone still images Requirements and guidelinesISO/IEC 10918-4, Information technology Digital compression and coding of continuous-tone still imag
26、es: Registration of JPEG profiles, SPIFF profiles, SPIFF tags, SPIFF colour spaces, APPn markers, SPIFF compression types, and Registration Authorities (REGAUT)ISO/IEC 10918-5, Information technology Digital compression and coding of continuous-tone still images: JPEG File Interchange Format (JFIF)3
27、 Terms and definitionsFor the purposes of this document, the following definitions apply.3.1bit streampartially encoded or decoded sequence of bits comprising an entropy-coded segment3.2block8 8 array of samples or an 8 8 array of DCT coefficient values of one component3.3bytegroup of 8 bits3.4coder
28、embodiment of a coding process3.5codingencoding or decodingINTERNATIONAL STANDARD ISO/IEC 18477-1:2015(E) ISO/IEC 2015 All rights reserved 1BS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E)3.6compressionreduction in the number of bits used to represent source image data3.7componenttwo-dimensional array
29、 of samples having the same designation in the output or display deviceNote 1 to entry: An image typically consists of several components, e.g. red, green and blue.3.8continuous-tone imageimage whose components have more than one bit per sample3.9discrete cosine transformDCTeither the forward discre
30、te cosine transform or the inverse discrete cosine transform3.10downsamplingprocedure by which the spatial resolution of a component is reduced3.11entropy-coded (data) segmentindependently decodable sequence of entropy encoded bytes of compressed image data3.12entropy decoderembodiment of an entropy
31、 decoding procedure3.13entropy decodinglossless procedure which recovers the sequence of symbols from the sequence of bits produced by the entropy encoder3.14entropy encoderembodiment of an entropy encoding procedure3.15entropy encodinglossless procedure which converts a sequence of input symbols in
32、to a sequence of bits such that the average number of bits per symbol approaches the entropy of the input symbols3.16grayscale imagecontinuous-tone image that has only one component3.17joint photographic experts groupJPEGinformal name of the committee which created this International StandardNote 1
33、to entry: The “joint” comes from the ITU-T and ISO/IEC collaboration.3.18legacy decoderembodiment of a decoding process conforming to Rec. ITU-T T.81 | ISO/IEC 10918-1 operating in baseline, sequential or progressive mode with a sample resolution of eight bits2 ISO/IEC 2015 All rights reservedBS ISO
34、/IEC 18477-1:2015ISO/IEC 18477-1:2015(E)3.19markertwo-byte code in which the first byte is hexadecimal FF and the second byte is a value between 1 and hexadecimal FE3.20marker segmentmarker and associated set of parameters3.21pixelcollection of sample values in the spatial image domain having all th
35、e same sample coordinatesNote 1 to entry: A pixel may consist of three samples describing its red, green and blue value.3.22precisionnumber of bits allocated to a particular sample or DCT coefficient3.23procedureset of steps which accomplishes one of the tasks which comprise an encoding or decoding
36、process3.24quantization valueinteger value used in the quantization procedure3.25quantizeact of performing the quantization procedure for a DCT coefficient3.26sampleone element in the two-dimensional array which comprises a component3.27sample gridcommon coordinate system for all samples of an image
37、 with the samples at the top left edge of the image having the coordinates (0, 0), the first coordinate increases towards the right, the second to the bottom3.28scansingle pass through the data for one or more of the components in an image3.29scan headermarker segment that contains a start-of-scan m
38、arker and associated scan parameters that are coded at the beginning of a scan3.30upsamplingprocedure by which the spatial resolution of a component is increased3.31vertical sampling factorrelative number of vertical data units of a particular component with respect to the number of vertical data un
39、its in the other components in the frame ISO/IEC 2015 All rights reserved 3BS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E)4 Symbols and abbreviated terms4.1 SymbolsX width of the sample grid in positionsY height of the sample grid in positionsNf number of components in an imagesi, xsubsampling factor
40、 of component i in horizontal directionsi, ysubsampling factor of component i in vertical directionHisubsampling indicator of component i in the frame headerVisubsampling indicator of component i in the frame headervx, ysample value at the sample grid position x, y4.2 Abbreviated termsASCII American
41、 Standard Code for Information InterchangeDC LowpassAC HighpassLSB Least Significant BitMSB Most Significant BitDCT Discrete Cosine Transformation5 Conventions5.1 Conformance languageThe keyword “reserved” indicates a provision that is not specified at this time, shall not be used, and may be specif
42、ied in the future. The keyword “forbidden” indicates “reserved” and in addition indicates that the provision will never be specified in the future.5.2 OperatorsNOTE Many of the operators used in this part of ISO/IEC 18477 are similar to those used in the C programming language.5.2.1 Arithmetic opera
43、tors+ Addition Subtraction (as a binary operator) or negation (as a unary prefix operator) Multiplication/ Division without truncation or rounding4 ISO/IEC 2015 All rights reservedBS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E)5.2.2 Assignment operators= Assignment operator5.2.3 Precedence order of o
44、peratorsOperators are listed below in descending order of precedence. If several operators appear in the same line, they have equal precedence. When several operators of equal precedence appear at the same level in an expression, evaluation proceeds according to the associativity of the operator eit
45、her from right to left or from left to right.Operators Type of operation Associativity(), , . Expression Left to Right Unary negation, / Multiplication Left to Right+, Addition and Subtraction Left to Right, = Relational Left to Right5.2.4 Mathematical functionsx Ceiling of x. Returns the smallest i
46、nteger that is greater than or equal to x.x Floor of x. Returns the largest integer that is lesser than or equal to x.|x| Absolute value, is x for x max or otherwise x.6 General6.1 General definitionsThe purpose of this clause is to give an informative overview of the elements specified in this part
47、 of ISO/IEC 18477. Another purpose is to introduce many of the terms which are defined in Clause 3. These terms are printed in italics upon first usage in this clause.There are three elements specified in this part of ISO/IEC 18477:a) An encoder is an embodiment of an encoding process. An encoder ta
48、kes as input digital source image data and encoder specifications, and by means of a specified set of procedures generates as output a codestream.b) A decoder is an embodiment of a decoding process. A decoder takes as input a codestream, and by means of a specified set of procedures generates as out
49、put digital reconstructed image data.c) The codestream is a compressed image data representation which includes all necessary data to allow a (full or approximate) reconstruction of the sample values of a digital image. Additional data might be required that define the interpretation of the sample data, such as the spatial dimensions of the samples. ISO/IEC 2015 All rights reserved 5BS ISO/IEC 18477-1:2015ISO/IEC 18477-1:2015(E)6.2 Functional overview on the decoding processThe high-level algorithm for d
